The probe covers about 420,000 pickups with 3.5-liter, six-cylinder engines from the 2013 and 2014 model years, according to documents posted Friday on the National Highway Traffic Safety Administration’s website.

The agency says it has 33 complaints about the problem, including drivers who report the pedals can suddenly go to the floor, with a complete loss of braking. Four drivers reported that the problem caused crashes, although there were no injuries. The agency reported that 31 of the complaints from F-150 drivers came in the past year, with 20 in the past seven months.

The NHTSA will continue to investigate and determine whether or not a recall is necessary.

Whether you drive an F-150 or not, it’s a good time for a refresher course on what to do should your brakes ever fail while you’re driving. It’s easy to panic in that situation and simply engage the emergency brake, but doing so too forcefully can send the car into a dangerous spin or even cause the car to roll over.

Here’s what to remember in case of a brake failure:

The very first thing you should do is downshift. If you’re in a vehicle with a manual transmission you can use it to slow the car considerably before gently applying the e-brake. In an automatic, downshift as far as possible. Your main goal is to pull over to the right while slowing down as much as possible yet staying in control of the car.

If you don’t have antilock brakes, pump the brake pedal to attempt to rebuild hydraulic pressure. If you do have antilock brakes, depress the pedal and hold it there in case pressure builds again.

Turn on your hazards and use your horn to alert other drivers that you have a problem and need clearance.

Check for debris under your brake pedal. It’s possible a water bottle, a soda can, or even a child’s pair of socks got wedged underneath and is not allowing you to brake.

From there, it’s a judgment call. Hopefully pulling off to the right, downshifting, and applying the e-brake is enough to stop the vehicle, but if not, you might be forced to aim for something soft. Obviously, avoid people and anything immovable (such as trees and concrete walls), but if there’s a row of hedges or pile of soft sand, use it.

Hopefully Ford and NHTSA solve this issue before anyone gets hurt, but in the meantime it’s a good idea to take your F-150 into a reputable brake shop for a system check-up.